Re: Why?

From: Steve <ThisOne_at_Aint.valid>
Date: Tue, 29 Jun 2004 21:32:34 +1200
Message-ID: <cbrcvj$osd$1@lust.ihug.co.nz>

omlet_at_omlet.org wrote:

> "Howard J. Rogers" <hjr_at_dizwell.com> wrote in message news:<40e00319$0$18666$afc38c87_at_news.optusnet.com.au>...
> 

>>"Alexander Skwar" <from_at_alexander.skwar.name> wrote in message
>>news:514cqrts7o0q.dlg_at_a.skwar.digitalprojects.com...
>>
>>>Am Mon, 28 Jun 2004 19:48:03 +1000 schrieb Howard J. Rogers:
>>>
>>>
>>>>"Alexander Skwar" <from_at_alexander.skwar.name> wrote in message
>>>>news:8iowpa5bgf2f.dlg_at_a.skwar.digitalprojects.com...
>>>>
>>>>>Hi!
>>>>>
>>>>>In the Oracle documentation, it's often suggested to use OFA to design
>>>>>where files are located. This suggests to create filesystems /u00,
>>
>> /u01,
>>
>>>>>/u02 ...
>>>>>
>>>>>What I don't get - suppose that my server supports RAID 5.
>>>>
>>>>No database should run RAID5.
>>>
>>>Why?
>>
>>Because RAID5 has a write penalty (so, Ok, a read-only database is probably
>>OK on RAID5).
>>
>>
>>>And why are you even suggesting RAID0? While RAID0 surely improves
>>>the speed, it also increases the risk of losing everything when just one
>>>disk goes faulty.
>>
>>What are archivelogs there for?
>>
>>My point was simply that RAID0 stripes, but without the write penalty.
>>Practically, you would really want RAID0+1, of course.
>>
>>But that's expensive, and one can forego the +1 component with a clear
>>conscience, provided your backup and archiving strategies are well thought
>>out.
>>
>>Regards
>>HJR

> 
> 
> HJR, you are really dumb!
> 
> Oracle data scenters use Network Appliance filers that are basically
> built with RAID4 technology - similar to RAID5.

It depends where you stick the parity (:

> 
> Please do not generalize! Most RAID boxes use large caches and do the
> writing using xx-stage algorithms your alikes are not fit to
> understand.

RAID= Redundant Array of Inexpensive Disks ( approx ). When you start looking at these SAN/NAS solutions, NA, EMC, whatever, they're not cheap any more. RAED?

> 
> to mirror; to stripe; to stripe mirrors; to mirror stripes; I bet your
> expertise with these are as shallow as your knowledge of access
> methods, optimizers and/or plans.

Offensively put, but I usually stripe striped mirrors if I can. >
> Apardon my response DOC! But please realize your reply is full of ....

If you need real performance, and continuous performance, then you need straight spindles. Caches, raid, it's all pretty irrelevant. I've built high performance databases that are spread over 100+ physical disks, using a fraction of their capacity, over many mirrored scsi channels, almost saturating their bandwidth. That's the only way to go. There's no rocket science, it's plain mathematics.

Now SATA is becoming well supported, you've got a 150MB/s bandwidth option that's relatively cheap, compared to SCSI disks. Stuff 4 disks on one of those, and you should get serious bang for your buck!

Steve Received on Tue Jun 29 2004 - 04:32:34 CDT